The present invention relates to a manufacturing method for semiconductor devices. More particularly, the present invention relates to a manufacturing method for semiconductor integrated circuits having improved yield and utilizing a flexible process sequence.
In the following background discussion, problems with conventional semiconductor manufacturing methods are described with reference to an oxidation process. The oxidation process is basic to semiconductor manufacturing methods. Generally, the oxidation process is one wherein the surface of a wafer is exposed to an oxidizing atmosphere at high temperature to thereby form an oxide film having uniform thickness and stable physical properties.
Of central concern to all semiconductor manufacturing methods is the question of yield. Again, using the example of an oxidation process, yield is typically measured by a comparison between the number of wafers which successfully finish the oxidation process, and the number of wafers which begin the oxidation process. Physical parameters such as oxide film thickness and resistance must be measured and controlled during the course of the oxidation process to improve yield. Proper electrical operation of the ultimately formed semiconductor device depends on the oxide layer satisfying the particular physical parameters set forth in a production specification. Accordingly, much attention is paid to improving the yield by minimizing changes to a successful manufacturing process. Yet, flexibility in the manufacturing processes is also highly desirable.
FIG. 1 is a flow chart illustrating a conventional method of forming and measuring an oxide film on a wafer. Referring to FIG. 1, the conventional manufacturing method comprises the steps of; placing the wafer in a quartz crystal holder, or "boat," in a reaction source cabinet (step 10), forming an oxide film having a constant thickness on the wafer by reacting the wafer with oxygen (step 11), measuring the thickness of the oxide film (step 12), measuring the contamination particles in the wafer (step 13), measuring sheet resistance of the wafer (step 14), eliminating the contamination particles, or cleaning the wafer with a solution of sulfuric acid (step 15), and removing the wafer from the boat (step 16).
Thus, in the conventional manufacturing method, the measuring steps are sequentially performed in a fixed order. In other words, the steps of thickness measuring 12, the contamination particle measuring 13, and resistance sheet measuring 14 are performed in sequence. Accordingly, even though equipment for measuring contamination particles and equipment for measuring sheet resistance can operate independently, they are, nonetheless, used only after the oxide film thickness has been measured. Such sequential operation results in delay during the manufacturing process and utilizing equipment inefficiently.